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Investigation of the substituent specific cross‐interaction effects on 13 C NMR of the CN bridging group in substituted benzylidene anilines
Author(s) -
Cao Chenzhong,
Lu Bingtao,
Chen Guanfan
Publication year - 2011
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/poc.1760
Subject(s) - substituent , chemistry , polar effect , chemical shift , carbon 13 nmr , stereochemistry , proton nmr , crystallography , medicinal chemistry
The substituent effect on 13 C NMR of the CN in benzylidene anilines XPhCHNPhY was investigated, in which the substituents X and Y are in p ‐position or in m ‐position of the two aromatic rings. The substituent effects including the inductive effects of X and Y, the conjugative effects of X and Y, and the substituent specific cross‐interaction effect were put into one model to quantify the 13 C NMR chemical shift δ C (CN) of the CN in XPhCHNPhY. A penta‐parameter correlation equation with correlation coefficient 0.9975 and standard error 0.17 ppm was obtained for 80 samples of compounds. The result shows that the substituents X and Y have an opposite effect on the δ C (CN). The electron‐withdrawing effects of X decrease the δ C (CN); while the electron‐donating effects of X increase the δ C (CN). In contrast, the electron‐withdrawing effects of Y increase the δ C (CN); while the electron‐donating effects of Y decrease the δ C (CN). A new substituent specific cross‐interaction effect parameter Δ σ 2 was proposed, which indicates that the most substituent specific cross‐interaction effect exists in the pair of max electron‐withdrawing group (EWG) and max electron‐donating group (EDG) or the pair of max EDG and max EWG. Further to verify the obtained correlation equation, 15 samples of model compounds were prepared and their δ C (CN) was measured in this work. The predicted δ C (CN) values with the obtained equation are in good agreement with the measured ones for these prepared compounds, which confirmed the reliability of the obtained equation. Copyright © 2010 John Wiley & Sons, Ltd.